Turkey and Russia have agreed to a cease-fire plan for all of Syria that was expected to come into force at mid-night Wednesday, Turkish state media said on Wednesday, as Ankara and Moscow tighten cooperation to find an end to the civil war.

The plan was to expand to the whole country a cease-fire that was brokered by Turkey and Russia earlier this month in the city of Aleppo to allow for the evacuation of civilians, the state-run Anadolu news agency said.

But in a speech in Ankara following the report, Turkish President Recep Tayyip Erdogan made no reference to the plan, while Kremlin spokesman Dmitry Peskov said he could not answer questions on an issue "about which I don't have enough information".

A Syrian rebel source, who asked not to be named, told AFP in Beirut that details still had to be submitted to the rebel groups, adding that there was no agreement as yet.

Like earlier plans brokered by the United States and Russia, it excludes "terror" groups, the agency said.

If successful, the plan could form the basis of political negotiations overseen by Russia and Turkey between the Damascus regime and the opposition in the Kazakh capital Astana, it added.

It was not immediately clear how and where the plan had been agreed on. Qatar-based Al-Jazeera said a new meeting is planned on Thursday in Ankara between Syrian rebels and Russia.